1. Field of the Invention
The present invention relates generally to methods for stimulating and activating cells, and more particularly, to methods to activate and expand cells to very high densities and to expand cells to very high numbers. The present invention also relates to compositions of cells, including activated and expanded T cells at high concentrations and expanded to high numbers.
2. Description of the Related Art
The T cell antigen receptor (TCR) is a multisubunit immune recognition receptor that associates with the CD3 complex and binds to peptides presented by the major histocompatibility complex (MHC) class I and II proteins on the surface of antigen-presenting cells (APCs). Binding of TCR to the antigenic peptide on the APC is the central event in T cell activation, which occurs at an immunological synapse at the point of contact between the T cell and the APC.
To sustain T cell activation, T lymphocytes typically require a second co-stimulatory signal. Co-stimulation is typically necessary for a T helper cell to produce sufficient cytokine levels that induce clonal expansion. Bretscher, Immunol. Today 13:74, 1992; June et al, Immunol. Today 15:321, 1994. The major co-stimulatory signal occurs when a member of the B7 family ligands (CD80 (B7.1) or CD86 (B7.2)) on an activated antigen-presenting cell (APC) binds to CD28 on a T cell.
Methods of stimulating the expansion of certain subsets of T cells have the potential to generate a variety of T cell compositions useful in immunotherapy. Successful immunotherapy can be aided by increasing the reactivity and quantity of T cells by efficient stimulation.
The various techniques available for expanding human T cells have relied primarily on the use of accessory cells and/or exogenous growth factors, such as interleukin-2 (IL-2). IL-2 has been used together with an anti-CD3 antibody to stimulate T cell proliferation, predominantly expanding the CD8+ subpopulation of T cells. Both APC signals are thought to be required for optimal T cell activation, expansion, and long-term survival of the T cells upon re-infusion. The requirement for MHC-matched APCs as accessory cells presents a significant problem for long-term culture systems because APCs are relatively short-lived. Therefore, in a long-term culture system, APCs must be continually obtained from a source and replenished. The necessity for a renewable supply of accessory cells is problematic for treatment of immunodeficiencies in which accessory cells are affected. In addition, when treating viral infection, if accessory cells carry the virus, the cells may contaminate the entire T cell population during long-term culture.
In the absence of exogenous growth factors or accessory cells, a co-stimulatory signal may be delivered to a T cell population, for example, by exposing the cells to a CD3/TCR ligand and a CD28 ligand attached to a surface, such as a bead or cell surface. See e.g., C. June, et al. (U.S. Pat. Nos. 5,858,358; 6,352,694;); C. June et al. WO 99/953823. While these methods are capable of achieving therapeutically useful T cell populations, increased robustness and ease of T cell preparation remain less than ideal.
In addition, the methods currently available in the art have not focused on short-term expansion of T cells or obtaining a more robust population of T cells and the beneficial results thereof. Furthermore, the applicability of expanded T cells has been limited to only a few disease states. For maximum in vivo effectiveness, theoretically, an ex vivo- or in vivo-generated, activated T cell population should be in a state that can maximally orchestrate an immune response to cancer, infectious disease, or other disease states. The present invention provides methods to generate an increased number of more highly activated and more pure T cells that have surface receptor and cytokine production characteristics that appear more healthy and natural than other expansion methods.
In addition, the present invention provides compositions of cell populations of any target cell, including T cell populations and parameters for producing the same, as well as providing other related advantages.